What is Public Domain?

What program did you use to make this?

MuseScore. It's an incredibly awesome piece of Open Source Software for creating music notation. Go download it now. Right Now!

If these songs are public domain, what's with the Creative Commons License?

The songs are public domain, my typesetting version of them is not. I'm giving it away for free, but I do not want others to sell my typesetting work.

How did you get the chords?

I guessed, used my best judgement, referenced the jazz Christmas list for the iReal Pro application, and just experimented. If you have a better progression for a song, send it to me and I'll include it.